Minimal docker-compose.yml for redmine+postgres ref: https://hub.docker.com/_/redmine/

docker-compose.yml

version: '2'

services:

  redmine:
    image: redmine
    ports:
      - 8080:3000
    environment:
      REDMINE_DB_POSTGRES: db
      REDMINE_DB_PASSWORD: example
      REDMINE_DB_USERNAME: redmine
    depends_on:
      - db
    restart: always

  db:
    image: postgres
    environment:
      POSTGRES_PASSWORD: example
      POSTGRES_USER: redmine
    restart: always